Stud for a tyre

ABSTRACT

The invention relates to a stud for a tyre comprising a socket-formed body portion ( 1 ), having at one end a hard metal peak ( 2 ) and at its other end a locking flange ( 3 ) retaining the stud in the tyre and being made of a light injection-mouldable material, such as plastic, the body portion ( 1 ) having a pin ( 4 ) extending towards the locking flange, with the tubular sleeve portion ( 5 ) of the locking flange fixed on top of this pin. The body portion ( 1 ) is conical so as to be clamped as a wedge into the corresponding conical sleeve portion ( 5 ).

[0001] The invention relates to a stud for a tyre comprising asocket-formed body portion having at one end a hard metal peak and atthe other end a locking flange retaining the stud in the tyre, and beingformed of a light material such as plastic, the body portion having apin extending towards the locking flange, with the tubular sleeveportion of the locking flange fixed on top of this pin.

[0002] As a rule, manufacturers of winter tyres seek to reduce tyrematerial, i.e. rubber mass, in order to achieve reduced weight of themass that is without suspension in the car and thus enhancedroad-holding characteristics. Winter tyres equipped with lighter studsalso cause less wear to the road surface material. As a result of themanufacture of lighter winter tyres, the stud-locking flange gets veryclose to the ply within a winter tyre. There is a distance of only 2-3mm between the stud-locking flange and the ply. As a result of this,again, the edge of the stud-locking flange has entailed such heavy wearof the tyre rubber under the tilting movements of the stud that theinternal ply has been damaged and even the tyre punctured.

[0003] There have been constant efforts to provide a stud solution thatis durable while being as light as possible. Plastic and aluminium studsare known, but they have poorer resistance than studs with a steel body.

[0004] Gravel and asphalt dust cause very rapid wear of the plastic oraluminium body surrounding the hard metal peak, so that the hard metalpeak may easily come off.

[0005] Such studs have been disclosed e.g. by FI patent specification77409 and US Pat. No. 3,831,655. The stud described in FI patentspecification 77409 is constituted of a metal stud body, around which acollar portion has been attached, with the stud flange portion formed atthe lower end of the collar portion. This type of stud involves theproblem of the metal stud body being strongly tapered towards the studflange portion. When the stud is then subjected to pressure in adirection parallel to the vertical axis of the stud, the metal stud bodywill act as a wedge that causes enlargement of the plastic collarportion. In the course of time, the plastic collar portion will beenlarged to an extent such that the metal stud body is detached from thecollar portion.

[0006] U.S. Pat. No. 3,831,655 discloses a stud, in which a shankportion made of metal has been connected to the bottom portion made ofan elastic material either by mechanical joining, gluing or vulcanising.In this stud model, the shank portion is clearly narrower than thebottom portion, so that the same apparatus intended for mountingconventional studs cannot be used for mounting this stud. The elasticmaterial of the bottom portion of the stud does not extend over theshank portion at all, or does so only over a short distance. Thisresults in low friction between the stud and the tyre, so that the studmay be detached from the tyre.

[0007] The purpose of the invention is to provide a stud of a new type,which is both resistant and light. The stud of the invention ischaracterised by the body portion being conical, so that it is clampedas a wedge into the corresponding conical sleeve portion.

[0008] The invention provides a very lightweight stud with adequatedurability characteristics. The weight of the stud may be even less thanhalf of the weight of a steel stud of equal size. The stud causes lesswear to the road surface. The stud is more silent, since it has lighterweight. The flexible locking flange is substantially retained inposition despite the tilting of the stud. Since the actual appearanceand dimensions of the stud do not differ from those of conventionalsteel studs, the studs can be fixed in the tyres using existingoperational equipment. Given the small size of the metal body portion,there will be very low waste percentage of raw material if themanufacture is carried out using turning. In addition, the plastic parthas proved to withstand abrasion against rubber better than a steelstud, and consequently the stud is better retained in the tyre.

[0009] Various embodiments of the invention are defined in the dependentclaims of the set of claims. The locking flange can receive forcesexerted on the hard metal peak of the stud, especially when the roadsurface is molten and the stud peak cannot bite into the snow mass orthe ice surface.

[0010] The invention is explained below by means of examples and withreference to the accompanying drawing, whose FIGURE shows the stud inpartial cross-section.

[0011] The stud consists of a socket-formed body portion 1, having ahard metal peak 2 at one end. At its other end, the body has a lockingflange 3 retaining the stud in the tyre. The locking flange 3 is made ofplastic. The stud body portion 1 has a pin 4 extending towards thelocking pin, the tubular sleeve portion 5 of the locking flange beingfixed on top of this pin. The body portion 1 is conical so as to beclamped as a wedge into the corresponding conical sleeve portion 5. Thebody portion 1 has a graded conical surface, its diameter being largerat the hard metal peak 2 than its end 4 at the locking flange 3. At thegraded location of the conical surface of the body portion 1 and theconical surface of the sleeve portion 5, there is a hollow annular space6, which allows the body portion 1 to be wedged deeper when pressingforces are exerted on the stud. The graded feature prevents the bodyportion 1, if loosened, from being unintentionally pressed into the tyreof the vehicle and causing puncture of this. The end of the sleeveportion 5 is open at the locking flange so as to allow the body portion1 to be wedged into it. The locking flange 3 has a convex recess 7 onits outer surface. The conical angle α relative to the central axis is3°.

[0012] The body portion 1 of the stud is not necessarily graded, it mayequally well be an even cone, however, in that case, the open space 8requires a collar to prevent the body portion from being pressed throughthe sleeve portion 5 into the tyre of the vehicle.

1. A stud for a tyre comprising a socket-formed body portion (1) havingat one end a hard metal peak (2) and at the other end a locking flange(3) retaining the stud in the tyre, and being made of a light materialsuch as plastic, the body portion (1) having a pin (4) extending towardsthe locking flange, with the tubular sleeve portion (5) fixed on top ofthe locking flange, characterised in that the body portion (1) isconical over substantially its entire length so as to be clamped as awedge into the corresponding conical sleeve portion (5).
 2. A stud asdefined in claim 1, characterised in that the conical surface of thebody portion (1) is graded so that its diameter is larger at the hardmetal peak than its end (4) at the locking flange (3).
 3. A stud asdefined in claim 1 or 2, characterised in having a hollow annular space(6) at the graded location of the conical surface of the body portion(1) and the conical surface of the sleeve portion (5).
 4. A stud asdefined in any of the preceding claims, characterised in that the end ofthe sleeve portion (5) is open at the locking flange (3).
 5. A stud asdefined in any of the preceding claims, characterised in having aconcave recess (7) known per se on the outer surface of the lockingflange (3).
 6. A stud as defined in any of the preceding claims,characterised in that the conical angle relative to the central axis is3°.
 7. A stud as defined in any of the preceding claims, characterisedin that the outer surface of the sleeve portion (5) is roughened.